Work principle of cold room for vegetables:
Fruits and vegetables enter the cold storage with a lot of heat of field and breathing. Besides, the heat leakage of the storage body, the field heat carried by the packing box, and the heat load generated by lighting, machinery and personnel operation need to be eliminated to maintain the low temperature in the cold storage. This process is completed by the state change of refrigerants. The working principle of mechanical refrigeration is to make use of the characteristic of absorbing heat when refrigerants change from liquid state to gas state, to make the state of refrigerants change mutually in the closed refrigerator system, to reduce the temperature of fruits and vegetables in the storehouse, and maintain the constant low-temperature conditions, to delay the aging of fruits and vegetables, extend the storage life and maintain the quality. At present, the most commonly used refrigerants are ammonia, halogenated hydrocarbon or chlorofluorocarbons. Ammonia is a commonly used refrigerant in large-scale refrigeration equipment. It has a low price, low boiling point temperature and great latent heat of gasification. However, it is easy to cause damage to the human skin and mucous membrane when leakage occurs. When water is contained, it is easy to corrode metal. When ammonia is mixed with oil and air to a certain concentration, there is a risk of explosion and combustion, which should be avoided. Because of these shortcomings, freon replaced freon in modern medium and small refrigeration equipment. China is actively taking measures to eliminate R12, R22 and other refrigerants currently commonly used, and widely research CFCs substitutes.